1. Field of the Invention
The present invention relates to a spectral image measurement apparatus in which a plurality of spectral elements for actuating a microelectrically-driven mechanical diffraction grating are arranged two-dimensionally, as well as to a method using the spectral image measurement apparatus.
2. Description of the Related Art
Light emitted from a substance is highly relevant to motion of electrons in the substance. Since spectra of the light are unique to the substance, the substance can be identified from the spectra.
JP-A-2001-99710 describes a “Method and system for estimating spectra of spectral reflectance” for a multiband image. Under this method, a conversion table has been prepared in advance for each of a plurality of channels of a multiband image consisting of a plurality of original images, wherein brightness values obtained by photographing a chart with known reflectivities are caused to correspond to the reflectivities. Brightness values of the original images of a multiband image obtained by photographing a subject are converted into reflectivities through use of the conversion table, thereby estimating spectra of spectral reflectance of the subject. According to this method, when a multiband image is photographed through use of a wavelength-variable filter and spectra of spectral reflectance of the photographed subject are estimated through use of the multiband image, a processing time required to determine estimated spectra is effectively shortened without involvement of a decrease in the estimation accuracy of spectra.
JP-T-10-511772 describes a “Fabry-Perot Filter Sensor” comprising: a first wafer; a sensor array formed on the first wafer; a ring which is formed on the first wafer and surrounds the sensor array; a second wafer; a first mirror formed on the second wafer; a bridge structure; a second mirror formed on the bridge structure; a Fabry-Perot cavity formed by means of attaching the bridge structure to the second wafer such that the first mirror opposes the second mirror; and an actuator which is formed on the bridge in close proximity to the second wafer and can change a distance between the first and second mirrors so as to tune the Fabry-Perot cavity. The Fabry-Perot Filter Sensor has a sealed, confined structure which is formed by placing the second wafer on a ring and housing an array formed from the Fabry-Perot cavity and the sensor and which enables monolithic microtuning. According to the Fabry-Perot filter sensor, a filtering wavelength is changed by means of controlling a distance between mirrors in the Fabry-Perot cavity.
JP-A-01-318929 describes a “Spectral Imaging Apparatus,” wherein the center of a diffraction grating for scattering light (hereinafter called a “light-scattering diffraction grating”) and the center of a diffraction grating for mixing light rays (hereinafter called a “light-mixing diffraction grating”) are aligned with a single drive axis, and wherein a wavelength is selected by means of rotating the diffraction grating around the drive axis. In this spectral imaging apparatus, the light-scattering diffraction grating and the light-mixing diffraction grating are aligned with each other. Hence, so long as the light-scattering diffraction grating and the light-mixing diffraction grating are set in a single operation so as to achieve optical symmetry by way of an intermediate slit, there is yielded an effect of the diffraction gratings being driven in a one-to-one relationship without causing a displacement or the like.